1. Field of the Invention
This invention relates to distributed control and automation of equipment. In one application, this invention may be used to control a coiled tubing unit. Depending on the control system configuration, equipment operation may be controlled by an on-site or a remotely located operator.
2. Description of Related Art
Real-time communication systems are the backbone of distributed control applications. The timeliness of real-time communications is important in a complex distributed real-time system. Use of a non-real-time network with a distributed control system that relies upon real-time communications presents challenges not addressed in the prior art. In a distributed control system, there is a need to integrate and bridge a non-real-time network with a real-time network to efficiently control equipment, for example on a plant floor. In combination, the non-real-time network, and the real-time network allow both local and remote control of equipment. This control architecture is readily expandable. The present invention has many different applications, but it finds particular application in the oil and gas industry and specifically to coiled tubing operations.
Coiled tubing is increasing in popularity as a method of drilling wells and conducting operations in an oil or gas wellbore. Coiled tubing is used as a continuous strand and is therefore easier and faster than conventional pipe in many applications, such as drilling wells, deploying reeled completions, logging high angle boreholes, and deploying treatment fluids. Coiled tubing is particularly useful in horizontal or multilateral wells.
Coiled tubing units or rigs have been used in the oil and gas industry for many years. They are used both on land and offshore for various types of operations. One common operation is often referred to in the industry as “sand cleanout”. During production, sand from surrounding formations may partially or completely plug a well. A coiled tubing unit will be brought to the wellsite to remove the sand from the well. The coiled tubing is run into the well and fluid is circulated down through the coiled tubing into the well. The fluid and the sand circulate up the annulus and out the wellhead where the sand is removed. This process frequently puts a well back into production or at least improves production. As mentioned above, coiled tubing units are used for various other operations including, but not limited to, matrix acidizing and nitrogen kickoff.
For most offshore operations, the coiled tubing unit has been modularized. The coiled tubing unit may be deployed from a ship or a platform. The coiled tubing unit equipment package typically consists of the following items: injector head, stripper, coiled tubing reel, power pack, control cabin, and the blow-out preventer (BOP). After all of this equipment had been delivered to an offshore platform, the coiled tubing unit must be set up and numerous hydraulic hoses must be connected. Equipment set up and take down will often take several hours on an offshore well. The coiled tubing job itself may run from several hours to several days. There is a need to reduce the amount of time it takes to set up and take down a coiled tubing unit on an offshore well. There is also a need to reduce the total weight of the coiled tubing equipment package sent to offshore operations.
To facilitate transportation to and from an offshore location, each of the following components is typically mounted on a separate skid: the coiled tubing reel, the injector head and stripper, the power pack, and the control cabin. The major components of the coiled tubing reel typically include the following: reel drum, reel drive system, levelwind assembly, reel swivel, and manifold. The major components of the power pack commonly include the following: engine, hydraulic pumps, pressure control valves, hydraulic reservoir, filters, strainers, heat exchangers, and hydraulic fluid. As previously mentioned, the control cabin is skid-mounted, although it may also be incorporated with the power pack. The control cabin contains all the necessary controls and instruments to allow the coiled tubing operation to be run by an on-site operator. A transparent window allows the operator to view the other components during the job. The major injector head components often include the following: hydraulic motors, drive chains, chain tensioners, gooseneck, weight indicator, stripper, and air brake. Various types of BOP's can be used, but quad BOP's are often encountered. Quad BOP's frequently include blind rams, shear rams, slip rams, pipe rams, and equalizing valves.
Coiled tubing units are deployed from trucks or trailers for land-based wells. An example of a mobile coiled tubing unit is described in U.S. Pat. No. 6,273,188, which is incorporated herein by reference. The coiled tubing unit includes a tractor and a trailer. The control cabin and power pack are mounted on the tractor. The trailer supports the coiled tubing reel, injector head, and a mast that can be raised during operations or lowered during transit. The mast supports the injector head above the well during operations. The BOP can also be transported on the trailer, or it can be transported to the well by a separate conveyance.
On both land-based and offshore-based coiled tubing units, numerous hydraulic hoses run between the different equipment components. There is a need to reduce the number of hydraulic hoses, hydraulic connections, and the number of skids for coiled tubing units. In general, fewer hydraulic hoses and connections reduce the number of oil leaks, which is economically beneficial as maintenance costs are reduced. Fewer oil leaks also benefit the environment. If the number of skids is reduced, it means less equipment cost for the operation.
U.S. Pat. Nos. 6,264,128 and 6,457,534 also describe apparatus and methods that may be used with coiled tubing units, namely a levelwind system for the coiled tubing reel and a method of reducing pipe fatigue by eliminating short movements, and are incorporated herein by reference.